The present invention relates to a brake shoe comprising a support having two opposite faces and a contour laterally exhibiting two opposite sides, a friction lining fixed to a first of the two faces of the support, said friction lining being adapted to cooperate frictionally with a rotary track in response to a clamping action exerted upon the second face of the support, each side of the support being adapted to cooperate in abutment against a lateral thrust shoulder.
When the shoe is new or lightly worn, the friction lining has a considerable thickness, with the result that it maintains the support sufficiently far from the rotary track for the side of the support always to find a correct abutment by the total thickness of that side, against the lateral thrust shoulder.
However, when the thickness of the lining has been considerably reduced by wear, it may occur that it no longer effects this correct positioning, and in this case it is possible for the side of the support to be applied against the thrust shoulder by only a part of its thickness, and it may escape completely from the thrust shoulder, which is worse.
The present invention relates more particularly to a brake shoe of the above-stated type, in which means are provided to prevent these defects, consisting in that the support exhibits in its marginal region adjacent to each side a protuberance projecting beyond the second face of the support, that is to say the face which is opposite the friction lining. Thus when the friction lining is heavily worn, this protuberance has the effect of maintaining correct contact between the side of the support and the lateral thrust shoulder.
However, these protuberances of the marginal regions of the support can cause inconvenience during the production of the shoes during baking of the shoes in the oven, when the shoes are stacked upon one another.
It is in fact important for this stacking to be effected by extensive contact zones in order to prevent deformations during pressure baking. This condition can no doubt be satisfied, despite the presence of the marginal protuberances, either by arranging wide chocks between the shoes, or by stripping the shoes marginally of lining. However, this results in a complication of production in the former case, and in a reduction of the friction performances of the shoe in the latter case.
The present invention has as its object a brake shoe of the above-stated type, which is free from these various disadvantages, the production of which is convenient, the positioning of which with reference to the lateral thrust shoulders remains correct even when the friction lining is worn, and in which the friction surface of the friction lining is very extensive, thus permitting excellent braking efficiency.